1. Field of the Invention
The present invention relates to arc quenching materials for high voltage electrical devices and equipment wherein under certain conditions of operation a high voltage electrical arc is produced that must be quenched to eliminate an undesirable current flow. More particularly, the present invention relates to the use of hexamethylenetetramine as an arc quenching material in devices such as high voltage fuses, circuit breakers, circuit interrupters, lightning arresters, and separable cable terminations.
2. Description of the Prior Art
It is well known in the art that to provide effective circuit interruption it is desirable to utilize an arc quenching material or substance in circuit interrupters and similar devices such as fuses to quench and suppress arcing during contact separation or fuse operation. Typically a trailer-liner configuration is used in circuit interrupters so that the arc is drawn into the annular space between the trailer and liner, each of which may be formed from an arc quenching material. The action of the gases produced by the trailer or liner on the confined arc tends to deionize the arc and force its extinction. In a high voltage fuse, typically a sleeve or liner surrounds the path of the arc during fuse operation. Many nonconductive materials are capable of being fabricated into the desired shapes, but the arc quenching current-interrupting effectiveness of such materials varies and many such materials are less effective in providing repeated arc quenching capabilities after initial use. Typically, circuit interrupters, excepting fuses, have utilized Plexiglas (methyl methacrylate polymer) as a trailer material and Plexiglas, horn fiber, or Delrin (polyoxymethylene) as a liner material.
It is well known in the art that in order to perform properly, an arc quenching material should have three immportant qualities. First, the material should be highly effective in quenching arcs produced over a wide range of electrical operating conditions. The properties of the materials should be such that an arc extinguishing gas is evolved quickly and effectively with a minimum consumption of arc extinguishing material. By minimizing the consumption of the arc quenching material, its operating life is prolonged.
Secondly, the arc quenching material and its solid fused residue should be relatively nonconductive to avoid reestablishing a current flow through the device after it has operated.
Finally, the arc quenching material should be capable of being molded or compounded with other materials into a composition having sufficient structural properties for the particular device in which the arc quenching material is employed.
Other properties of the arc quenching material may also be important, such as thermal stability. It is also desirable that the arc quenching gas evolved be neither obnoxious nor toxic.
It has been discovered that hexamethylenetetramine is an effective and suitable arc quenching material.